Skip to Main Content

Library of Congress (LC) Call Numbers

How to read Library of Congress (LC) call numbers.

Parts of the LC Call Number

Most books in the SPU Library are organized by Library of Congress (LC) call number as a method to group like subjects together on library book shelves. Each book has a unique identification number (or shelf address); this number is found on the spine of books (or sometimes on the front cover) and in the library's catalog records. 

These unique shelf location numbers allow the books to be organized alphabetically by Library of Congress (LC) subject letters and numbers, grouping like subjects together for easier browsing. (See complete list of LC subject classification categories for details.)

Here's a sample call number, with an explanation for each line:

QE -   indicates the general subject area; presented on the shelf in alphabetical order

862 -  number line which indicates more specifically the subject area; presented on the shelf in numerical order within the QE section

.D5 -  combination of letters and numbers that often represent the author's last name; presented on the shelf in alphabetical then decimal order

E539 - second combination of letters and numbers to further refine; not always present

2006 - year of publication; presented chronologically on the shelf

Sometimes the library location is also indicated above the call number (for example REF, for the Reference Collection, or JUV, for the Juvenile Collection).

How to Find a Book on the Library Shelf

When you are looking for a book, always start with the top line of the call number.  Remember, books are arranged alphabetically by this top line. For example, all BR numbers are together, after BP and before BS, and all B’s come after all combinations of A and before all combinations of C, like this:

B . . . BP, BR, BS, . . . C, CA, CB . . .

When books have identical letter lines, look to the number line next. Books are ordered using whole numbers on this line. For example:

Example of call number order: F3, F21, F221, F2021, F3021

When the top two lines are identical, look to the third line. Books are first ordered alphabetically; books with the same letter in the third line are then arranged by decimal number (not whole number.) The following call numbers are in correct order:

Example of call number order: PN70 .P441, PN6231 .E29, PN6231 .E295, PN6231 .F44

When the top three lines are identical, look to the fourth line. If it contains a letter followed by numbers, items are organized by letter and, within each letter, by decimal number. (Note that this works just like the line above it, treating the numbers as a decimal even though there is no visible decimal point.) The following call numbers are in correct order:


Example of call number order: QE862 .D5 L22, QE862 .D5 L4571, QE862 .D5 L461, QE862 .D5 M37

Multiple editions of a book will have the same call number, except for the last line, which will be the year of publication. Later years are shelved after earlier ones.

Some call numbers will include lines at the bottom to describe the volume, issue or part of the larger publication. These are shelved in alphabetical or numerical order, whichever is used. The following example is in correct order:

Example of call number order: QK115 .R538 v.2 pt.2, QK115 .R538 v.3 pt.1, QK115 .R538 v.3 pt.2


The information on this page is adapted from the University of Michigan guide of the same name: Library of Congress (LC) call numbers


Creative Commons

Except where otherwise noted, this work is subject to a Creative Commons Attribution 4.0 license. For details and exceptions, see the Library Copyright Statement.